The demilitarization and disposal of surplus and reject propellants, explosives, and energetic materials has been a requirement over the years. The most commonly employed method of disposal involves open burning and open destruction (OB/OD) of hazardous munitions and ingredients. Large scale reclamation of specific ingredients from propellants and warheads has been pursued only when the manufacturing cost or strategic importance of a particular ingredient was sufficiently high to justify the added recovery expenses. For example, U.S. Pat. No. 4,376,666 disclosed a cost effective method to recover n-hexylcarborane (NHC) from solid rocket propellants at a cost of only a fraction of its manufacturing costs. This method, although cost effective for the reason stated, resulted in diverting a major amount of remaining propellant ingredients to waste for ultimate disposal using traditional approaches.
Recent Environmental Protection Agency (EPA) restrictions limiting OB/OD of hazardous wastes and munitions poses an enormous problem which touches all phases of the propulsion industry. Civilian directed Government agencies, such as NASA, and all of the military organizations and their DoD contractors are now experiencing the impact of these new regulations. Developments in the Intermediate-Range Nuclear Forces (INF) arms negotiations have underscored the urgency to identify acceptable methods to demilitarize large rocket motors. Conventional means of destruction, such as launch-to-destroy, static firing or open burning, present extreme environmental sensitivities. Demilitarization methods, which can meet the new EPA regulations, are not currently available. The most widely discussed alternative to current OB/OD methods involves the use of water-jet propellant cutting followed by oxidizer solvation and reclamation using a traditional solvent extraction system.
Attempts to extract, recover, and recycle ammonium perchlorate oxidizer from large amounts of water effluents associated with large motor demilitarizations have also proved uneconomical, and the technology has not been reduced to industrial practice. Energy costs associated with water effluent treatments and ammonium perchlorate recrystallization are too great in comparison to the less than $1 cost per pound of commercial grade ammonium perchlorate.
The propulsion industry would welcome a method to demilitarize, extract, and recover propellant ingredients as well as to recover miscellaneous rocket motor hardware for recycling. The method should be one which is adaptable for recycling the material used to demilitarize, extract and recover propellant. The method would be particularly attractive if recovery of the propellant ingredients and hardware results in a return of high economic value to the system while minimizing any adverse effect to the environment.
An innovative method for propellant demilitarization, reclamation, and hazardous waste minimization that takes advantage of the "gas-to-liquid" and "liquid-to-gas" phase transition, which can occur during the compression and expansion of all gases, would have distinct advantages over existing methods. Specifically, a gas when pressurized to its liquified state and functions as a nontraditional liquid solvent would be highly desirable in a method to demilitarize, extract, and recover the major ingredient from composite propellants. The use of a nontraditional liquid solvent with a demonstrated solvating capability for the extraction of ammonium perchlorate oxidizer, the major ingredient in nearly all large solid rocket motors, represents a radical departure from the OB/OD and water-based removal/extraction methods currently employed or proposed by cognizant personnel associated with demilitarizing rocket motors and other munitions. An added benefit of utilizing a liquidified gas as an extraction solvent, as described in this disclosure, is that the demilitarization process can be nonpolluting, inexpensive, and environmentally acceptable.
Therefore, an object of this invention is to provide a method which employs a solvating medium to efficiently demilitarize, extract, and recover ammonium perchlorate in high yield from a solid propellant composition.
Another object of this invention is to employ a solvating medium which has a high solubility for ammonium perchlorate while in a liquified state, but when expanded to its natural gaseous state under reduced or ambient pressure conditions, the solvating medium quantitatively and rapidly releases all solids or liquid materials which were initially retained as the solute of the system thereby making recovery efficient and rapid.